Towards Self Reliance in Navigation-IRNSS

Indian Regional Navigation Spacecraft System (IRNSS) is the Indian navigation system which envisages establishment of regional navigation system using a combination of GEO and GSO spacecraft. IRNSS system is expected to provide position accuracy of better than 20 m over Indian region and an area extending about 1500 sq km around India. IRNSS constellation consists of three Geostationary Earth Orbit (GEO) spacecraft and four spacecraft in Geosynchronous orbit inclined at 29 deg. It would provide two types of services, namely, Standard Positioning Services (SPS) - provided to all users - and Restricted Services (RS), provided to authorize users.

Three satellites of IRNSS will be at 5 deg inclination called GEO satellites. Three of the GEO satellites will be placed at 32 deg E, 83 Deg E and 131.5 deg E. The four GSO satellites will be placed in inclined orbit with longitude crossover of equatorial plane at 55 deg E and 111.75 deg E. GSO satellites are placed in two planes with the planes being 180 deg apart.

IRNSS -1E carries two types of payloads – navigation payload and CDMA payload. The navigation payload operating in L5-band and S-band will transmit navigation service signals to the users and also has a highly accurate Rubidium atomic clock. The ranging (CDMA) payload consists of a C-band transponder which facilitates accurate determination of the range of the satellite. It also carries Corner Cube Retro Reflectors (CCRR) for laser ranging.

IRNSS-1E, the fifth navigation satellite of the seven satellites of the Indian Regional Navigation Satellite System (IRNSS), was successfully launched by Polar Satellite Launch Vehicle, in its 33rd flight (PSLV-C31) on January 20, 2016 at 09:31 Hrs (IST) of Satish Dhawan Space Centre SHAR (SDSC SHAR), Sriharikota, the spaceport of India.

PSLV-C31 was the thirty second consecutively successful mission of PSLV and the eleventh time ‘XL’ configuration was flown. Its predecessors, IRNSS-1A, 1B, 1C and 1D which were launched by PSLV-C22, PSLV-C24, PSLV-C26 and PSLV-C27 in July 2013, April 2014, October 2014 and March 2015 respectively.

Like its predecessors, IRNSS-1E had a lift-off mass of 1425 kg. The configuration of IRNSS-1E is similar to that of IRNSS-1A, 1B, 1C and 1D. All the five satellites are functioning satisfactorily from their designated orbital positions.

PSLV-C31 lifted-off from the Second Launch Pad with the ignition of the first stage, After a flight of about 18 minutes 43 seconds, IRNSS-1E Satellite was injected to an elliptical orbit of 282.4 km X 20,655.3 km inclined at an angle of 19.21 degree to the equator (very close to the intended orbit) and successfully separated from the PSLV fourth stage.

After injection, the solar panels of IRNSS-1E were deployed automatically and the Master Control Facility (MCF) at Hassan took control of the satellite and performed the initial orbit raising maneuvers consisting of one maneuver at perigee (nearest point to earth) and three at apogee (farthest point to earth). For these maneuvers, the Liquid Apogee Motor (LAM) of the satellite was used, thereby finally placing it in the Geosynchronous Orbit at its designated location. IRNSS-1E now located in the Geosynchronous Orbit at 111.75 deg East longitude with 28.09 deg inclination.

Preliminary health checks of the satellite revealed its normal health. Subsequently, MCF performed the initial orbit raising maneuvers by repeatedly firing the Liquid Apogee Motor (LAM) on-board the satellite for a total duration of around 4620 seconds. In-Orbit Testing (IOT) of IRNSS-1E was carried out when the satellite reached its desired longitude of 111.75deg after STAQ maneuvers. Navigational and CDMA Payloads were tested during IOT and test results were comparable with ground test data. After IOT, satellite was declared for regular use.

The remaining two satellites of this constellation, namely, IRNSS-1F and 1G are scheduled to be launched by PSLV by the end of March 2016, thereby completing the entire Phase 1 IRNSS constellation.